Pump control means



Julie 1951 Filed 1, 1945 Patented June 5, 1951 UNITED STATES PATENT OFFICE PUMP CONTROL MEANS Application August 21, 1945, Serial No. 611,854 In Great Britain June 5, 1944 1 Claim.

This invention relates to internal combustion prime movers, particularly for aircraft, of the kind having associated therewith a centrifugal or other air compressor and fuel governing means whose action, at least in part, is correlated with the rate of rotation of the compressor. A well known effect which accompanies the action of a centrifugal air compressor is that when the mass-air flow is reduced to some particular value (termed the surge point) an abrupt decrease or severe fluctuation of the delivery pressure is apt to occur, this effect being known as surging. This effect depends at least in part on the density of the air passing through the compressor, and the object of the present invention is to enable the fuel governing means (one of the functions of which is to prevent the surge point being reached), to compensate satisfactorily the effect of variations of air density due to temperature changes.

The accompanying drawing is a diagrammatic part sectional side view illustrating one form of the invention. As shown in the drawing we employ a variable-delivery liquid fuel pump b of the swash plate type similar to that described in the specification of Patent No. 2,403,371. The rotary body part (not shown) of this pump is adapted to be driven in any convenient manner by the prime mover to be supplied with liquid fuel by the pump. In one end of the casing of the pump b is formed a cylinder 71 having closed ends. Within the cylinder p is arranged a piston q loaded by a spring T and extending from one side of this piston is a rod 8 connected to the swash plate (not shown) of the pump. The end of the cylinder 10 at the piston-rod side of the piston q is in free communication with the pump outlet through a passage 29, and this end of the cylinder also communicates with the other or outer end of the cylinder (which contains the spring r through a restricted passage u The outer end of the cylinder p is provided with a vent 12 When this vent v is closed, the liquid pressures at the two sides of the piston q are equal, and the spring r then moves or tends to move the piston in the direction for increasing the pump output. But when the vent o is opened, the liquid pressure in the outer end of the cylinder p falls and the piston q is moved by the predominating fluid pressure in the inner end of the cylinder against the action of the spring 1 for reducing the output of the pump 11 The vent o in the outer end of the cylinder 19 is controlled by a lever m which is responsive to the outlet and inlet pressures of the compressor It, the latter being driven by and serving to supply air to the prime mover. The x is secured at a position intermediate its ends to a diaphragm M which serves as a fulcrum, for the lever, and forms a dividing partition between two chambers l5, It. The chamber I 5 is pro-- vided with an inlet 11 which forms a seating for a closure member w on the adjacent end of the lever 0: and which is connected by a pipe or passage l8 to the vent o in the outer end of the cylinder 12 The chamber 15 may also be adapted for connection to the pump inlet. Arranged within the other chamber I6 is a second lever I9 which is pivoted at a position intermediate its ends to this chamber. The chamber 16 also contains a compression spring 20 adapted to act on one end of the second lever I9, and an evacuated capsule 2| adapted to act on the other end of the second lever in opposition to the spring. Interposed between the spring loaded end of the second lever l9 and the adjacent end of the first lever :0 is an abutment piece 22 through which the levers can serve under the action of the spring 20 to move the closure member w towards its seating, and thereby restrict flow of liquid through the vent 2J Secured to the chamber I6 is a sub-chamber 23 bounded at one side by a flexible diaphragm 24, the latter serving as a dividing partition between the chamber and subchamber. This sub-chamber23 is adapted for connection bya pipe or passage 25 to the outlet of the compressor 13, and a thrust piece 26 is arranged between the diaphragm 24 and the first lever x at a position nearer to the fulcrum of r' this lever than the abutment piece 22 above mentioned, the arrangement being such that the compressor outlet pressure is transmitted through the diaphragm and associated thrust piece to the first lever in the direction for moving the closure member 20 away from its seating against the action of the spring 20. The chamber I6 is adapted for connection by a pipe or passage 21 to the inlet of the compressor I3, so that the evacuated capsule 2| serves to reduce the effect of the spring 26 on the first lever 3: when the compressor inlet pressure falls, and vice versa. The abutment piece 22 between the levers x 19 is connected by a link 23 to any convenient adjusting mechanism 29 whereby the abutment piece can be moved towards or away from the lever fulcrums to satisfy any desired value of N/ /T where N is the rate of rotation of the compressor I 3, and T is the absolute temperature of the air entering the compressor.

As soon as the lever x is unbalanced by variation of the compressor outlet or inlet pressure the fuel delivery of the pump will be appropriately adjusted.

Instead of acting on the lever :5 in the manner Shown in Figure 2 the compressor outlet and inlet pressures may act on two evacuated capsules connected to the lever at appropriate distances from its fulcrum, or may act on the lever through two diaphragms or plungers.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is:

In a fuel supply system forsupplying liquid fuel and air to a prime mover of the type having a variable delivery fuel supply pump and a rotary air compressor, a fuel governing means comprising in combination a fluid pressure responsive member, a chamber containing said member, a passage for admitting an unrestricted supply of pressure fluid to said chamber at one side of said member, a restricted passage for admitting pressure fluid to said chamber at the other side of said member, a pressure fluid vent situated at the side. of said chamber to which fluid is admitted through said restricted passage, a valve controlling said vent, a lever for actuating said valve, a second fluid pressure responsive member for moving said lever in the direction for opening said valve, means consisting at least in part of a third fluid pressure responsive member for moving said lever in the direction for closing said valve, and means for exposing the second and third fluid pressure responsive members respectively to the pressures at the outlet and inlet sides of said compressor.

STANLEY GEORGE HOOKER.

ERNEST ANSLEY WATSON.

RICHARD JOSEPH IFIELD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 21,758 Foisy Apr. 1, 1941 2,177,098 Doe et a1 Oct. 24, 1939 2,273,670 Udale Feb. 17, 1942 2,292,125 Ifield Aug. 4, 1942 2,403,371 Ifield et a1 July 2, 1946 2,407,013 Ifield Sept. 3, 1946 2,424,035 Ifield July 15, 1947 2,429,005 Watson et al Oct. 14, 1947 2,440,663 Ifield Apr. 27, 1948 2,450,535 Watson et a1. Oct. 5, 1948 

